MOD_CSINWD Module

This subroutine does an inwards integration of llmax functions f with an extended 3-point-simpson :

$$\begin{equation} f_{int}\left(ll,i\right) = \int_{ir}^{ir_{max}}f\left(ll,i'\right)di' \end{equation}$$

The starting value for this integration at ist - 1 is determined by a 4 point lagrangian integration, coefficients given by m. abramowitz and i.a. stegun, handbook of mathematical functions, nbs applied mathematics series 55 (1968)

Modified for functions with kinks - at each kink the integration is restarted